US2287727A - Automatic phonograph - Google Patents

Description

June 23, 1942. R CRANMER 2,287,727

AUTOMATIC PHONOGRAPH Filed May 15, 1941 7 2 Sheet-Shet 1 Mal 5, @anmer June 23, 1942. R. s. CRANMER AUTOMATIC PHONCGRAPH Filed May 15, 1941 2 Sheets-Sheet 2 operation between Patented 'June 1942 I Richard S. Cranmer, Philadelphia, Pa., assignor to Philco Radio and Television Corporation, Philadelphia, Pa., a corporation of Delaware Application May 15, 1941, Serial No. 393,633

11 Claims.

This invention relates to automatic phonographs of the type wherein the record-changing cycle is initiated by a trip mechanism responsive to the rate of movement of the tone pickup over the record being reproduced.

More particularly, the invention relates to that type of trip which is adapted to function at the I end of a recording, as the pickup stylus moves out of thereproducing grooves into a spiral of greater pitch, or an eccentric groove; or in the event that the tone-arm moves too rapidly'at any time during the playing of 'a recording. By way of example, the trip itself may be of the type which is triggered by the more rapid than normal movement of the pickup and which, in turn, serves to trigger a suitable mechanism adapted to lift the pickup and swing it off the record, in order that a succeeding recording may be placed upon the turntable.

Many of the trip mechanisms of this general character, which has been employed heretofore, have been of t. ,more or less complicated nature,-

embodying a large number oi moving parts. The use of .many parts not only raises the manufacturing cost of the trip mechanism, but has an additional disadvantage in that the trip mechanism, normally in operation, requires considerable energy ior its actuation. This energy must come from the movement of the tone-arm, which movement is, in turn, brought about by the co-,

the stylus and the record groove. Thus, it can be very light stylus pressures now in use; that there may be a tendency toward bad tracking, that is. the needle point will often ride up one side of the groove and thereby distort the recorded signal.

The principal object of the present invention is to overcome the aforesaid difllculties by theprovision of a trip mechanism which is simple to manufacture, embodies relatively few moving parts, and which'requires very little energy to operate its trip restraining means.

I A further object of the invention resides in the provision of a member moving in a predetermined relation to the movement of the tone-arm; which member carries with it a novel switch. the contacts of which remain open during normal movement'of the pickup, and close when said pickup moves more rapidly across the record.

The invention also has for an object the provision of a velocity responsive trip mechanism embodying a switch, wherein the closing of the switch contacts completes an electrical circuit to to initiate operation of the tone-arm lifting mechanism.

The invention may be fully understood by reference to the following description taken together with the accompanying drawings.

In the'drawings,

- Fig. 1 is a perspective view of a phonograph pickup assemblyembodying the invention;

Fig. 2 is a perspective view taken from a different angle, particularly illustratingthe tonearm lifting device, with certain parts broken away for the sake of illustration;

Fig. 3 is a detail sectional view of-the'switch mechanism; and

V Fig. 4 is-a diagrammatic illustration, of the switch-controlled circuit. a

Referring more particularly to the drawings,

, in Fig. 1 is illustrated an automatic phonograph seen, especially with the comprisingthe usual-turntable I, on which is carried one or more sound records 2, fitted over a central spindle 3. The turntable is driven by suitable means (not shown) preferably taking the form of an electric motor. and such transmission elements as may be desirable. Av tone-arm 4 is swingingly mounted in cooperative relation with the turntable, as by means of the pivot support generally indicated by the reference character 5. Freedom for raising and lowering movements of the tone-arm is provided by a further pivot 5a (see Fig. 2). Thus, as is customary, the tone-arm is adapted to move laterally over the record and may also be raised or lowered with respect thereto. A base plate '6 provides com- 'crank 8 pivotally attached to a member 9, as at l0. Member 9, in turn, is pivoted to the rotatable support 5 by a pin indicated at H. one arm of the bell crank 8 has a downwardly extending actuating portion l2, while the other arm I4 is 50, pinned to an "upwardly extending lift member IS an electrically-operateddevice. which is a p by means of a pivot IS. The lift member l5 carries at its upper end a. rod II adapted to engage the tone-arm. The lift assembly, comprising member l5 and rod ll extends through anopenmg l8 in the supporting baseplate 6, to permit men support for both the turntable and the. tonehorizontal swinging of the lift mechanism as the support 5 rotates, in response to movement of the tone-arm across the record.

The lifting mechanism is actuated by means of a pivoted arm l6 whose operation will be described later. to state that when the depending portion ll! of bell crank 8 is moved by arm I! to the right, as viewed in Fig. 2, the lift member I5 is raised, bringing the upper end of rod I'I into engagement with the tone-arm. Continued upward movement of the lift-arm l5 causes the tone-arm 4 to be lifted off the record 2. In the mean- "time, however, the weight of the tone-arm acts -a means for moving the raised tone-arm so as to condition it for repeated playing of the record or the playing of a succeeding record. The present invention is not directly concerned with this latter means and for,the present purpose a brief description thereof will suffice. The member .9 has anextending arm 20 on the end of which there is provided a cam follower 2| which is adapted to seat in an eccentric cam groove provided inthe upper face of a disk 22 which is geared to the turntable shaft by means of the gear 23 on the disk, gear 24 on the turntable shaft,- and an intermediate gear 25. The cam groove acting through arm 26 serves to rotate the tone-arm support 5, thereby rotating the tone-arm about its vertical pivot. Since this mechanism for rotating the tone-arm through an arc when it is in raised position is well known, and since the present invention is not directly concerned with'it, it is unnecessary .to illustrate or describe the said mechanism in further detail. Hence, it has been deemed-unnecessary to illustrate the cam groove in the upper surface of disk 22. v

The present invention is concerned, however, with an additional'function of the rotating disk 22 which results from spaced projections 26 on the underside of the peripheral portion of the disk. The purpose of these projections will be described later. I

Referring again to Fig. 1, it will be seen that the arm I9 is shaped as illustrated and is pivoted at 21 to a supporting'bracket (not shown) on the said arm. The arm H has turned-up lugs 3| and 32 which serve as stops for the element 30 which is normally maintained against stop 32 by means of spring 33, secured at one end to a lug 34 on element 30 and at its other end to a lug 35 on arm 16. The arm I9 is urged For the present, it is sufficient bracket 28. When the arm I8 is latched in inoperative position as shown in Fig. l, the element 30 is out of the path of cam 26, and, therefore, the cam is free to rotate without actuating arm l9.

Latch member 36 is adapted to be actuated by the novel trip means now to be described, which is responsive to the rate of movement of the tone-arm over a record.

At the lower end of tone-arm support column 5 is fixed an arm-42, constrained to move with tone-arm 4 and generally underlying the same. The outer end of arm'42 is forked as at 4343 and extends over an arcuate plate 44, which may be fixed to the frame of the machine, as at 45. A second arcuate plate 46 overlies the forked end of arm 42, and is carried by an arm 41 which is centrally pivoted as at 46, to the machine framing 26. The opposite end of arm moving upper plate 46 out of engagement with block 60. Thus, at regular intervals, determined by the speed of rotation of disk 22 and the spacing of projections 26 thereon, plate 46 is pulsed upwardly and permits block 56, under the influence of spring 6|, to inch" forward in the direction of rotation followed by arm 42. "A spring may be provided as at 52, to insure firm contact between the pulsing plate 46fand the cooperating block 50, when roller'45 is no't in" contact with one of the projections 26;

With especial reference to Fig. 3, it will be seen that a switch box, generally designated by the reference character 53, is mounted between the forked ends 4343 of arm .42.-

box comprises relatively movable parts, one of which is rigidly connected to one of the arms 43 as by means of lug 54, while the other part is carried by the block 56. Block 50,'in turn, is slidably mounted on a short shaft 55 which is fixed to the opposite fork arm. Electrical contact prongs 56 and 51 are carried by the respective parts of the switch box, and the spring 5| is interposed between the two sections. It will be obvious that suitable insulation should be provided between the contact prongs and the associated box structure, or the box itself may be made of insulating material.

The switch contacts 66 and 51 serve to control .a solenoid or electromagnetic device 58 whose toward operative engagement with cam 29 by a spring 36 secured at one end to the lug 35 and at its opposite end to a lug 31 which may be fixed to the frame of the machine. 1 Normally, however, the arm I 9 is latched in inoperative position against the action of spring 36 by a latch member 36 which is pivoted at 39 to a supporting bracket 26. The .latch member has a hook-like end which engages a small knob 46 on arm l6. The latch member 36 is urged to latching position by spring 48, one end of which is anchored to the stationary support or However, when one of the projections 26' strikes the roller 46, arm 47 is rotated slightly about its pivot 48, thereby the tone-arm moves over the record, the arm 42 moves correspondingly. During the intervals between the "successive actuations of plate 48 through the medium of projections 28, the block 50 is frictionally held by plates 44 and 46, and

the movement offorkarms 43 toward the right, as viewed in Fig. 3, compresses spring l and brings contact prongs 56 closer to prongs 51. When plate 46 is raised by one of the projections 28, block 50 is freed and is moved by. spring II, carrying prongs EIfurther away-from. prongs I I and re'establishing the normal distance between the prongs. i

The above-described parts of the tripping mechanism are soconstructed that the latch 38 is not tripped .as long as the tone-arm moves over the record at itsjnormal rate of speed while the stylus is traversing the sound grooves of the record. During such normal movementof the tone-arm, the slight movement of the switch contacts toward each other, is insu'filcient to bring them" into contact. Each time arcuate plate 46 is pulsed, as above described, the block aasmar sponsive to the rate of movement of the pickup, which is' of such a nature as to be very table and a tone-arm adapted to move across a 50 inches forward, under the influence of spring 5i, thusmaintaining the, contacts separated. Since the intervals at which the plate 48 is pulsed, are fixed by the spacing of projections 26, and the speed of rotation of disk 22 driven from the constant speed turntable drivingmeans,

the operation of latch tripping solenoid is dependent entirely upon .the rate of movement of the tone-arm as it traverses'a record.

As set forth above, the purpose of the tripping device is to operate the tone-arm lifting answinging mechanism at the end of a record, andalso to interrupt the playing of a record by lifting the tone-arm in the event that the tone-arm moves too rapidly at any time. of the tripping mechanism at the end of a record is brought about when the'stylus'l engages a groove of steeper pitch, which causes rapid inward movement of. the tone-arm. ,At such time, or in the event that the-tone-arm should move laterally too rapidly at any time; arm l2, and hence that part of the switch box which is fixed thereto, is moved sufliciently betweensuccessive disengagements of plate 46, to permit the contacts 58 and 51 to engage one another- This trips the latch member", as described above, and thereby permits arm H to move to operative position under the influence of spring 38. This The operation recording, a trip mechanism comprising a member adapted to movewith the tone-arm, a pair of electrical contacts carried by said member, means urging said contacts toward the open po- 'sition, holding means preventing movement of one of said contacts therebycausing one of said contacts to approach the other as said tone-arm traverses the recording, and means operable by the turntable periodically to release said holding means at intervals bearing a predetermined timed relation to the normal speed of said tone-arm.

2. In an automatic phonograph having a tonearm, a trip mechanism comprising a 'member adapted to move with the tone-arm, a second member adapted to move both with the first member and with respect thereto, a cyclicallyoperated pulsing member adapted to engage and release said second member at intervals bearing a timed relation to the speed of advance of the tone-arm, whereby said two members periodi- -of' advance cally'move with one another and with respect to each other, and trip control means operable by thereiative movement of said members.

3. A construction in accordance with claim 2, wherein the phonograph turntable includes a plurality of cam projections, and wherein the pulsing member comprises a pivoted plate having a cam follower adapted'to be struck and moved by the cam projections.

' In an automatic phonograph having a tonearm, a tripmechanism comprising a member adapted to move with the tone-arm, a second 7 member adjacent said first member and adapted brings the curved edge of cam follower into the path of a shoulder 8i oncam 29. Cam fol-,

lower 30 is thereby caused to move away from stop 32 into engagement with stop-3i. Since the element 30 can move no further, the cam 29 v causes pivotal movement of arm f9, bringing the curved end thereof into engagement with arm l3 of the tone-arm lifting device, as shown in Fig. 2. The cam 29 maintains the arm I! in its" effective position during the movement of the tone-arm to the beginning of a record by means of the arm 20, as above described. After the tone-arm has been thus moved, the cam 29 releases elefnent 3B, permitting it to move back tion shown: inFigr-2, the stylus being depositedat the beginning of'a record.

It will be seen that the invention provides a trip mechanism for automatic phonographs re-.

to move intermittently in the same direction as said first member, means urging said members apart, a cyclically-operating member adapted to engage and release said second member at timed intervals, whereby saidtwo' members periodically move with respect'to each other, and trip control means operable by the relative movement of said members.

5. In an automatic phonograph having a tonearm adapted to moveover a recording, a trip mechanism operable by said tone-arm, said trip mechanism comprising a first memberdriven by said tone-arm continuously in one direction, a

second member adjacent said first member and adapted to move intermittently in the same di- I rection as said first membenineans'urging said members apart, means for periodically restraining said second member against movement,

whereby said-two members periodically move toward and away from each other, and trip control means operable by the relative movement of said members.

6. In an automatic phonograph, a turntable supporting a sound record, atone-arm carrying a stylus adapted toengage: the record grooves, means for lifting said tone-arm to remove said stylus from the record, a pivoted member operposition, and means responsive to the rate ofmovement of said tone-arm for tripping said latching means when the tone-arm moves in'exv cess of a predetermined rate, said tripping means including an electromagnetic latch-releasingdevice, a member movable with the tone-arm, a pair of electrical contacts carried by said member and adapted to energize said latch-releasing device when said contacts are closed, means urging said contacts toward the open position, holding means adapted to prevent movement of one of said contacts with said member thereby. causing one of said contacts to approach the other, means operable by the turntable periodically to release said holding means at intervals bearing such a predetermined timed relation to the normal speed of advance of said tone-arm as to insure that said contacts will remain open during advance of the tone-arm at a normal playing rate, and that said contacts will close upon advance of the tone-arm at a greater-than-normal rate.

7. In an automatic phonograph of the type having mechanism for raising a tone-arm and swinging it oi! oi the record and a latch for normally holding said mechanism inoperative, a. latch-tripping mechanism responsive to the rate of movement of said tone-arm, comprising an electromagnetic device adapted to release the latch, a member movable with the tone-arm, a pair of elements carried by said member and carrying electrical contacts, the contacts being adapted to energize said electromagnetic device when in the closed position, spring means urging said elements away from each other, frictional means adapted to hold one of said eletone-arm, that under such normal speed conditions said elements are moved apart under the influence of the spring means before the contacts have closed.

8. In an automatic phonograph having a turntable and a tone-arm, a trip mechanism comprising a pair of electrical contacts adapted to' move with the tone-arm, resilient means'urging said contacts toward the open position, a pair of plates adapted to restrain one of said contacts,

thereby preventing movement of said contact with the tone-arm and causing the other contact to approach the restrained contact against the action of said resilient means, andmeans for.

.periodically releasing the restraint of said plates fiat intervals bearing a predetermined timed relation to the normal speed of advance-of said tone-arm 9. In an automatic phonograph having a tonearm adapted to move across a recording and means for lifting the tone-arm from the recording, a trip mechanism for controlling said lifting means, comprising a switch having relatively movable contact members, means operable by said predetermined periods of substantially equallyspaced time relation, and means operable by the engagement of said members for initiating operation of said lifting means, whereby said lifting means is actuated only in the event that the g5 tone-arm moves at a rate sufficiently great to enable said one member to overtake and engage said other member.

10. In an automatic phonograph having a turntable and a tone-arm, a trip mechanism comprising an electrical contact member, a second electrical contact member, means tending to move the second contact toward the first contact when the tone-arm moves across the turntable, means tending to move said first contact away 85 from said second contact, and means for alternately and periodically restraining and releasing said first contact against the action of the means tending to move it away from said second contact, whereby the distance between said two 0 contacts will be alternately diminished and increased.

11. In an automatic phonograph having a turntable and a tone-arm, a trip mechanism comprising an electrical contact member, a second 5 electrical contact member, means tending to move the second contact toward the first contact when the tone-arm moves across the turntable, resilient means tending to move said first contact away from said second contact, and means for alternately and periodically restraining and releasing said first contact agalnst the action of the resilient means, whereby the distance between said two contacts will be'alternately diminished and increased.

RICHARD s. CRANMER.

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